New Artificial Gravity Tests in Space Could Help Astronauts

A view of a NASA-provided Short Radius Centrifuge at UTMB in Galveston is reminiscent of similar equipment from 40 years ago when astronauts were training for the initial giant leap to the Moon.

Credit: NASA/JSC

New plans for artificial gravity tests in space using
centrifuges may hold the key to helping future astronauts ward off the
debilitating loss of muscle and bone due to weightlessness on long missions to
asteroids or the moon under NASA's revised space exploration plan.

The new
NASA budget proposed by President Obama not only sets
sights on long-duration missions, but also extends the lifetime of the
International Space Station. Upgrades for the space station "could include
a centrifuge to support research into human physiology," according to a summary
by the Office of Management and Budget.

Space station residents currently rely upon different
exercises to keep themselves fit for the eventual return to Earth.
But a spinning centrifuge device could create artificial gravity, which
simulates the gravitational tug a planet, like Earth, has. The giant spinning
device will give astronauts a healthy break from the weightlessness of space.

"You can try to treat each of the effects of
weightlessness system by system, with certain pills for bone loss and certain
exercise regimens for the muscles," said Laurence Young, an aeronautics
and astronautics engineer at MIT in Cambridge, Mass. "Or you can treat the
root cause of weightlessness by restoring gravity."

NASA's earlier focus on sending astronauts back to the
moon meant shorter-duration spaceflight and less urgency to develop artificial
gravity. The U.S. space agency focused on traditional countermeasures, such as modifying
squats or other exercises to counteract bone and muscle loss, according to
Justin Kaderka, an artificial gravity researcher working with Young at MIT.

Now the prospect of longer missions to more distant
destinations has once again raised the appeal, if not necessity, of artificial
gravity.

Recreating Earth gravity

One of Young's Japanese colleagues filed a proposal with
the Japan Aerospace Exploration Agency months ago to launch a human centrifuge
to the International Space Station. The device could ideally take up the
diameter of a space station module with a radius as wide as 6.6 feet (2
meters).

Astronauts would lie down on or strap themselves to one
end of the centrifuge arm or frame, and experience artificial gravity while the
device spins. A rider could also provide the human power to spin the centrifuge
by pedaling bicycle-style.

"If you have two arms that'd work nicely,"
Kaderka told SPACE.com. "Cycling would give an aerobic workout, and
the other person not cycling could do resistance exercises like squats or
presses."

The riders on a two-arm centrifuge could then switch off
on exercises and on powering the device. A vibration isolator would absorb any
residual vibrations that might otherwise disturb the rest of the space station,
according to the proposal.

Spin me right round

Earth experiments suggest that artificial gravity works
just as well as traditional countermeasures to prevent long-term weightlessness
from affecting human cardiovascular health, Kaderka said. He drew that
conclusion after reviewing 75 experiments done over the past 40 years, as his
MIT master's thesis.

But Kaderka also found that more research is needed to
assess whether artificial gravity can work its wonders upon muscle and bone.
That's partly because researchers must resort to expensive, long-term bed-rest
studies to really see the effects
on muscle and bone.

One human centrifuge did go into space with the STS-90
"Neurolab" mission aboard the space shuttle Columbia in 1998. But the
astronauts spent barely an hour in total testing out the centrifuge during the
16-day mission, which still left the effectiveness of artificial gravity open
to question.

"It'd be amazing to get hard data on how artificial
gravity is an effective countermeasure in space," Kadera said.

Artificial gravity research has suffered in the latter
half of the past decade because of NASA's budget issues and earlier focus on
returning astronauts to the moon. No funded centrifuge studies on human physiology
currently exist in the United States or among most of its international space
partners, Kaderka noted.

Taking the next step

NASA shut down its artificial gravity studies at the Johnson Space Center in Houston several years ago ? a decision that resulted in much lost momentum
for researchers, according to Young. But both he and Kaderka seemed optimistic
that the space agency's new direction would lead to resurgence in artificial
gravity work.

Getting a centrifuge up to the space station would do
much more than help answer the question of artificial gravity's effectiveness
in space, or putting renewed interest in complementary Earth experiments. It
would also allow researchers to start fine-tuning the exact conditions needed
to for artificial gravity to work.

"One of the hopes is to have the [centrifuge] protocol
down to within an hour or so of being spun, because that's roughly how much the
astronauts spend doing exercise," Kaderka explained.

Other questions include debate over how fast should the
centrifuge spin, setting the ideal artificial gravity level, as well as how
much time astronauts will need to spend aboard the centrifuge to see its
benefits. Then there are also biomedical questions about whether astronauts
encounter problems with dizziness
or vertigo, and whether the centrifuge is both effective and
enjoyable.

Of course, researchers can begin tackling some of those
questions if they can get renewed NASA funding for Earth experiments as well.
Otherwise they could be in for a long wait until they see a centrifuge launch
to the space station.

"Hopefully we won't have to wait as long as having
data come back from a space station centrifuge," Kaderka said.